4l80e transmission

Hi all, I won't be posting here much, but I wanted to share that I have started a build thread over at the Pacific Engineering Forum to document my big build. I am taking a stock 97 Chevy Tahoe with a 5.7 liter engine with a thrown rod and reforming it into a sports mobile affectionately...

I noticed recently that my 4l80E transmission is revving up between 2nd and 3rd gear, worse when you accelerate harder. Is this a servo or maybe a seal? Any help would be greatly appreciated.